1. Field of the Invention
The present invention illustrates a power-up sequence protection circuit, and more particularly, a power-up sequence protection circuit for avoiding an unexpected power-up voltage.
2. Description of the Prior Art
Non-volatile memory is a type of memory that retains information it stores data even when no power is supplied to memory blocks. Some examples include magnetic devices, optical discs, flash memory, and other semiconductor-based memory topologies. Non-volatile memory can be categorized in electrically addressed systems (i.e., read-only memory) and mechanically addressed systems (i.e., hard disks, optical disc, magnetic tape, holographic memory, and such). Specifically, since non-volatile memory does not require its memory data to be periodically refreshed, it is commonly used for secondary storage or long-term consistent storage.
To drive an internal circuit of the non-volatile memory, various voltages are required for controlling or enabling the non-volatile memory sequentially. For example, a device voltage is inputted to the internal circuit for controlling a core circuit of the internal circuit. An input/output (I/O) voltage is inputted to the internal circuit for controlling input/output devices of the internal circuit. A program voltage is inputted to the internal circuit for controlling an access operation of the internal circuit. These voltages can be appropriately adjusted for driving the internal circuit of the non-volatile memory. Specifically, in the internal circuit, the device voltage (i.e., control circuit power) has to be powered up first.
In the internal circuit of the non-volatile memory, when an unexpected voltage is powered up (i.e., such as an unexpected program voltage is powered up) before the device voltage is powered up, the internal circuit is operated under an abnormal state, leading to power leakage and circuit disturbance of some components.